Streptosolen jamesonii 'Yellow', a new host plant of Potato spindle tuber viroid

Recent identification of Potato spindle tuber viroid (PSTVd) in various solanaceous ornamental plants in The Netherlands (Verhoeven et al., 2007) has drawn attention to the phytosanitary risks posed by imported mother plants. In this context, one leaf per plant from a total of 100 and 200 plants of Streptosolen jamesonii 'Yellow' and S. jamesonii 'Orange', respectively, were collected from plants originating in Israel and tested for PSTVd before entry into The Netherlands. The leaves were tested by real-time reverse transcription-polymerase chain reaction (RT-PCR) (Boonham at al, 2004) in 24 samples consisting of 12 to13 leaves. Isolated RNA was first diluted by an additional 10-fold to reduce inhibition. All 8 samples of the 'Yellow' cultivar produced Ct values between 28.0 and 31.3, whereas no amplification was observed for the 16 samples from S. jamesonii 'Orange'. To confirm identification and for subsequent sequencing, positive samples were tested by RT-PCR using PSTVd primers developed by Shamloul et al. (1997). All samples yielded amplicons of the expected size, i.e. approximately 360 nt. Because these primers may also amplify isolates of Tomato chlorotic dwarf viroid, a definite identification of PSTVd was based on the nucleotide sequence. The amplicon sequence (357 nt) was, with the exception of one nt, identical to a previously reported PSTVd sequence from Solanum jasminoides (Verhoeven et al., 2007; NCBI GenBank accession number EF192393) and Solanum rantonetti (Di Serio 2007; NCBI GenBank accession number EF459700). The sequence of the new PSTVd isolate from S. jamesonii was submitted to NCBI GenBank (Accession number EF580923). S. jamesonii 'Yellow” is a new host plant species of PSTVd and may act as a symptomless carrier of the viroid.